1. Field of the Invention
The present invention relates generally to an electronic apparatus and a circuit board for use in, e.g., a notebook-sized personal computer of a type supplying an electric power to loads in response to a plurality of action modes, and more particularly to an electronic apparatus and a circuit board designed to supply an electric power to the loads consisting of a plurality of groups in response to the action modes including the supply of power and the suspension.
2. Description of the Related Arts
Referring first to FIG. 1, a typical circuit is shown which feeds electric powers for action to a diversity of devices, i.e., loads incorporated in notebook-sized personal computers. In response to action modes, a DC/DC converter 100 serving as a DC power source feeds powers to the loads, e.g., a CPU module 102, a memory module 104 and CD-ROM module 106. In this event, the CPU module 102 includes a CPU and an HDD, and the memory module 104 includes an SDRAM and a VGA. The CD-ROM module 106 includes a CD-ROM player and an AMP. A power supply line 114 from DC/DC converter 100 diverges at a node into a line 116 and a line 118 which connects via an FET switch circuit 112 to the CD-ROM module 106. The line 118 further diverges into a line 120 and a line 122 which connect to the CPU module 102 and the memory module 104, respectively. FET switches 108, 110 and 112 are disposed on the lines 118, 120 and 116, respectively, and are on/off controlled by a control circuit 115 in such a manner as to conform the action modes. The control circuit 115 provides an on/off control of the DC/DC converter 100 as well. Once a power switch of a personal computer is acted upon, the control circuit 115 provides a control of the activation mode to turn on the DC/DC converter 100 as well as to turn on all of the FET switches 108, 110 and 112, allowing powers to be supplied to all of the CPU module 102, the memory module 104 and the CD-ROM module 106 for their respective actions. When a suspend switch is operated in those actions, the control circuit 115 provides a suspend mode to turn off the FET switch 110 to halt the supply of power to the CPU module 102. In this state, a resume switch is operated so that the FET switch circuit 110 is turned on and restored to its pre-suspension state. The migration to the suspension mode could be designated by software.
By the way, in the conventional electronic circuit supplying electric powers to the loads in response to the action modes, a relatively large amount of current of, e.g., 3 amperes flows through the CPU module 102 whereas a small amount of current of, e.g., 0.3 ampres flows through the memory module 104. As a result of this, 3.3 ampere current, the sum of the 3 ampere current through the CPU module 102 and the 0.3 ampere current through the memory module 104, flows through the FET switch circuit 108. This results in a deficiency that a combined current to two loads flows through the FET switch circuit 108, causing a greater power loss. Furthermore, the FET switch circuit 108 needs to be an PET having a large current capacity so as to allow a passage of as large a current as 3.3 amperes therethrough, which results in an increased circuit mounting area as well as in increased costs.
According to the present invention there are provided an electronic apparatus and a circuit board which have contrived paths for supplying an electric power to loads in response to action modes so as to allow a minimal amount of current to flow through switch circuits turning on/off the supply of electric power, thereby reducing the power loss as well as the circuit mounting area.
A first aspect of the present invention provides an electronic apparatus for feeding an electric power to loads in response to a plurality of action modes, the electronic apparatus comprising an on/off controllable power source circuit for providing an electric power as its output to the loads; a first switch circuit disposed on a power supply line extending from the power source circuit to a first load; a second switch circuit disposed on a power supply line to a second load diverging from the input side of the first switch circuit; and a control circuit for providing an on/off control of the power source circuit, the first switch circuit and the second switch circuit in response to the plurality of action modes. In this manner, separate power supply lines are disposed which extend from the power source to the respective loads and which are each provided with a switch circuit, so that each switch circuit allows only a flow of current determined by one load supplied with an electric power, whereby the sum of currents to a plurality of loads is prevented from flowing into a specific switch circuit even though the on/off state of the switch circuit has changed depending on the action modes, thereby reducing the power loss of the switch circuit disposed on the power supply line and diminishing the current capacity to reduce the size of the elements and parts used, for the reduction of the circuit mounting area.
The control circuit in a first action mode turns on the power source circuit, the first switch circuit and the second switch circuit to permit a supply of electric power to the first and second loads. The control circuit in a second action mode turns on the power source circuit and the second switch circuit but off the first switch circuit to permit a supply of electric power to only the second load. Herein, the first action mode is a normal action mode, and the second action mode is a suspend mode permitting a supply of electric power to only a specific, limited load. The first load includes a CPU, and the second load includes a memory.
The electronic apparatus of the present invention further comprises a third switch circuit disposed on a power supply line to a third load diverging from the line on the input side of the first switch circuit, and the control circuit further provides an on/off control of the third switch circuit in response to the action modes. In this event, the control circuit turns on both the power source circuit and the third switch circuit in a third action mode permitting a supply of electric power to the third load in the state of the first action mode, the second action mode or a stop mode. The third load includes a CD drive for replaying a CD-ROM or a CD for example, and the control circuit defines the third action mode independently of the first action mode, the second action mode or the stop mode so as to allow a replaying action of the CD drive.
A second aspect of the present invention provides a circuit board for feeding an electric power to loads in response to a plurality of action modes, the circuit board comprising a first switch circuit disposed on a first power supply line extending from a power source circuit to a first load; a second switch circuit disposed on a second power supply line to a second load diverging from the input side of the first switch circuit; and a control circuit for providing an on/off control of the power source circuit, the first switch circuit and the second switch circuit in response to the plurality of action modes. In this event as well, the circuit board further comprises a third switch circuit disposed on a third power supply line to a third load diverging from the line on the input side of the first switch circuit, and the control circuit provides an on/off control of the third switch circuit in response to the plurality of action modes.
The above and other objects, aspect, features and advantages of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.